The domain list-manage.com is for a MailChimp server, and the URLs returning this error are for a MailChimp integration method that they stopped supporting a few years ago, though apparently many integrations already set up with these old URLs continued to work for some time, up until now. All this error notification means is that MailChimp is no longer accepting buyer info via this old integration method; our system is otherwise processing affected orders normally (issuing links, sending emails, logging the order details, etc.)

If you are no longer using MailChimp with E-junkie, you can simply delete the obsolete notification URL from your E-junkie settings, depending on the Subject of the notification emails: